A semiconductor laser device (LD) as an optical semiconductor device is used a lot as a light source in an optical communication system and a light source in information processing equipment. A visible radiation semiconductor laser is used as a light source in information processing equipment such as a document filing system as well as in CD and DVD equipment, laser printers, POS, and bar-code readers. As a structure of the semiconductor laser device (optical semiconductor device), a so-called ridge structure is well known (for instance, JP-A No. 5696/2005 and JP-A No. 17269/1999).
JP-A No. 5696/2005 describes that the step for forming the ridge stripe structure includes the steps of first etching and second etching. The step for first etching is an etching process where the second conducting type second and third cladding layers are etched by dry etching to leave a prescribed thickness. The step of second etching is an etching process where the second conducting type second cladding layer which is left with a prescribed thickness is etched to the etching stop layer and removed by wet etching. Moreover, the same document describes that a tailing part appears in the etching stop layer even though the ridge stripe structure becomes a vertical mesa structure by dry etching, and with this a problem arises that the luminescence property of the laser device is deteriorated.